I debated whether to put this in a "things to do" or "tourist traps," because to call it a tourist trap is somewhat harsh. There's nothing wrong with the lake itself, and it's a nice enough downhill walk from Kandersteg... but the entrance fee is CHF 5 for access to the lake via some short paths. As I said, the lake is nice, with an impressive blue hue, but it certainly isn't worth 5 Francs to see, especially with all of the other spectacular scenery in the area.
Unique Suggestions: First, walk there from Kandersteg. From the train station (with your back to the tracks), turn left and follow the signs to "Blausee/Frutigen." It's about a 90 minute hike, then the path to Blausee splits off.
Next, when you go to the lake, take a look at the modest museum that gives some explanation of how the Blue Lake became... well, blue.
Finally, take a look at the trout swimming around in the lake -- it's always a hit with children. Plus, one of these guys may well be your dinner tonight (the fish, not the children! :).
Fun Alternatives: Head to the Oeschinensee. It's much more scenic, and it's free.
Kandersteg is not really much of a town, in fact the only reason why I love it so much is because of the proximity and easy access to Berneroberland. The town itself is pretty much a tourist hell hole because in the winter Ksteg is a popular ski resort. Although there were hardly any tourists in the summer when I was there, the mass souvenier shops selling chocolates and swiss army knives, hiking shops, and overpriced restaurants remain.
Unique Suggestions: get outside of town and experience nature.
We didn't visit the Blausee this time - once is enough. This small lake and trout farm is a bit overhyped for what it is IMHO. If you must go its a ten-minute drive north of Kandersteg, just off the main valley-floor road. There is also a train stop here so its eaily reached that way. Another option is to hike for an hour or so along the valley - that would pad out a half day trip here. Its privately owned so you have to pay for the pleasure of entering here to then hire a small row boat or have a meal at the restaurant.
Unique Suggestions: At least with a boat ride here you should be able to see the petrified fir trees which have lain on the bottom of the lake for hundreds of years.
Fun Alternatives: Other views are too hemmed in here by the thick trees - a much prettier alternative is to go to Oeschinensee above Kandersteg.
This is a couple of miles from Kandersteg and widely promoted. As the "Rough Guide" warns we were a bit "underwhelmed". Nice place for a picnic but if you have a car there are a lot more exciting places to visit - for instance Oeschinensee (actually for that you walk to the cable car station from town).
Unique Suggestions: Take a picnic.
Fun Alternatives: Oeschinensee.